The respiratory quotient of the excess metabolism of exercise

In recent years much controversy has been aroused as to whether the body uses carbohydrate alone in order to provide energy for the recovery process from muscular exercise, or whether the other foodstuffs can be used directly for this purpose. One of us (Furusawa), from a study of the respiratory quotient of the excess metabolism, concluded that carbohydrate is alone responsible for supplying the energy for short-lived exercise, while other food-stuffs must be converted into carbohydrate before they are so used by Muscle (1). This conclusion has been contested by several workers and no means of reconciling the different observations was apparent. A new factor, however, has recently been discovered, in the intensity of the exercise undertaken. This may help to explain the discordant results of the various workers on this subject. During the spring of 1927 Furusawa, Hill and Parkinson (2) made a large number of observations on the gaseous exchang of "sprint running," in order to determine the "mechanical efficiency" of this form of very severe exercise. Incidentally the results revealed a most remarkable phenomenon in respect of the respiratory quotient of the excess metabolism resulting from such exercise. Briefly stated, the excess respiratory quotient showed a wide divergency from unity (1·2 to 1·6). It has often been observed that the respiratory quotient rises above unity during or immediately after severe exercise. The assumption of the "blowing off" of CO2 would adequately meet these cases. On the other hand the high "excess" respiratory quotient, which we will now describe, has never been described before. In fact, however, this new phenomenon appeared invariably, and as it seems now most conspicuously, in many experiments, before its existence was recognised.